Pulmonary carcinosarcoma and carcinoma: report of a case studied by electron microscopy, with critical review of the literature.

About 50 cases of pulmonary carcinosarcoma have been reported in the French and English literature. They have rarely coexisted with non-pulmonary neoplasms, never with other primary lung tumors. This report describes a 68 year old male smoker with a carcinosarcoma developing in the right upper lobe, one and a half years after a left upper lobectomy for a scar adenocarcinoma. By light microscopy, there was an admixture of adenocarcinomatous, chondrosarcomatous, and malignant spindle cell and giant cell areas. Electron microscopy showed well and poorly differentiated epithelial, smooth muscle and cartilaginous elements. This case is of interest because of its occurrence with another lung primary tumor; the specific diagnosis was made by transthoracic needle aspiration; and of the ultrastructural features. In the literature, carcinosarcomas have been divided into an endobronchial type, in which the carcinomatous component is squamous in 91% of cases, and a peripheral type, in which it is glandular in 50% of cases; the sarcomatous component shows no such correlation with type. The theories for the histogenesis of these tumors revolve around the concept that the carcinoma is the principal element, and the sarcomatous or stromal change secondary. Therefore, on the basis of this case, and of our literature review dealing with the pathology, clinical features and histogenesis of these tumors, we suggest that carcinosarcomas share important features with lung carcinomas.